scholarly journals The scaffold protein EPG-7 links cargo–receptor complexes with the autophagic assembly machinery

2013 ◽  
Vol 201 (1) ◽  
pp. 113-129 ◽  
Author(s):  
Long Lin ◽  
Peiguo Yang ◽  
Xinxin Huang ◽  
Hui Zhang ◽  
Qun Lu ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Protein Aggregates ◽  
Scaffold Protein ◽  
Receptor Complex ◽  
Interacting Proteins ◽  
Physiological Conditions ◽  
Receptor Complexes ◽  
Atg Proteins ◽  
Cargo Receptor ◽  
Autophagic Degradation

The mechanism by which protein aggregates are selectively degraded by autophagy is poorly understood. Previous studies show that a family of Atg8-interacting proteins function as receptors linking specific cargoes to the autophagic machinery. Here we demonstrate that during Caenorhabditis elegans embryogenesis, epg-7 functions as a scaffold protein mediating autophagic degradation of several protein aggregates, including aggregates of the p62 homologue SQST-1, but has little effect on other autophagy-regulated processes. EPG-7 self-oligomerizes and is degraded by autophagy independently of SQST-1. SQST-1 directly interacts with EPG-7 and colocalizes with EPG-7 aggregates in autophagy mutants. Mutations in epg-7 impair association of SQST-1 aggregates with LGG-1/Atg8 puncta. EPG-7 interacts with multiple ATG proteins and colocalizes with ATG-9 puncta in various autophagy mutants. Unlike core autophagy genes, epg-7 is dispensable for starvation-induced autophagic degradation of substrate aggregates. Our results indicate that under physiological conditions a scaffold protein endows cargo specificity and also elevates degradation efficiency by linking the cargo–receptor complex with the autophagic machinery.

scholarly journals Ref(2)P, the Drosophila melanogaster homologue of mammalian p62, is required for the formation of protein aggregates in adult brain

2008 ◽  
Vol 180 (6) ◽  
pp. 1065-1071 ◽  
Author(s):  
Ioannis P. Nezis ◽  
Anne Simonsen ◽  
Antonia P. Sagona ◽  
Kim Finley ◽  
Sébastien Gaumer ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Protein Aggregates ◽  
Adult Brain ◽  
Aggregate Formation ◽  
Ubiquitinated Protein ◽  
Physiological Conditions ◽  
Binding Domains ◽  
Ubiquitin Binding ◽  
Autophagic Degradation

p62 has been proposed to mark ubiquitinated protein bodies for autophagic degradation. We report that the Drosophila melanogaster p62 orthologue, Ref(2)P, is a regulator of protein aggregation in the adult brain. We demonstrate that Ref(2)P localizes to age-induced protein aggregates as well as to aggregates caused by reduced autophagic or proteasomal activity. A similar localization to protein aggregates is also observed in D. melanogaster models of human neurodegenerative diseases. Although atg8a autophagy mutant flies show accumulation of ubiquitin- and Ref(2)P-positive protein aggregates, this is abrogated in atg8a/ref(2)P double mutants. Both the multimerization and ubiquitin binding domains of Ref(2)P are required for aggregate formation in vivo. Our findings reveal a major role for Ref(2)P in the formation of ubiquitin-positive protein aggregates both under physiological conditions and when normal protein turnover is inhibited.

scholarly journals RETRACTED: Peptide-induced formation of protein aggregates and amyloid fibrils in human and guinea pig αA-crystallins under physiological conditions of temperature and pH

2019 ◽  
Vol 179 ◽  
pp. 193-205 ◽  
Author(s):  
Anbarasu Kumarasamy ◽  
Sivakumar Jeyarajan ◽  
Jonathan Cheon ◽  
Anthony Premceski ◽  
Eric Seidel ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Amyloid Fibrils ◽  
Protein Aggregates ◽  
Physiological Conditions

scholarly journals Nuclear acceptor sites for androgen-receptor complexes in seminal-vesicle epithelium

1980 ◽  
Vol 192 (1) ◽  
pp. 41-47 ◽  
Author(s):  
M J Weinberger ◽  
C M Veneziale
Keyword(s):  
Seminal Vesicle ◽  
Nuclear Dna ◽  
Steroid Receptor ◽  
Assay Method ◽  
Scatchard Analysis ◽  
Receptor Complex ◽  
Receptor Complexes ◽  
Constant Slope

An assay method in vitro was developed and applied to quantify acceptor binding of steroid-receptor complexes in nuclei from isolated epithelium of guinea-pig seminal vesicle. Steroid-receptor complex prepared from 1-day-castrated animals was incubated with purified nuclei from 1-28 day-castrated animals in a medium containing 0.15 M-KCl. Free and bound steroid-receptor complexes were measured and the data were submitted to Scatchard analysis. With nuclei from 1-day-castrated animals the Kd for binding of cytosolic [3H]dihydrotestosterone-receptor complexes was found to be 0.83 × 10(-10) M and the capacity for binding was 0.35 pmol/mg of nuclear DNA. Scatchard analysis consistently disclosed only a single line of constant slope and gave the same kinetic constants for nuclei obtained from animals castrated up to 28 days before assay. Administration of 2 mg of dihydrotestosterone, 3 alpha-androstanediol or androsterone or 100 microgram of oestradiol-17 beta 1 h before killing of the 1-day-castrated animals that provided the nuclei resulted in a significant decrease in nuclear acceptor binding of the steroid-receptor complex compared with untreated animals. Thus our assay method disclosed nuclear acceptor sites that may be involved in responses to androgens (and oestrogens) in vivo. We conclude that there is a class of nuclear accept or sites of high affinity and limited capacity that may be occupied by steroid-receptor complexes in vivo.

scholarly journals Endothelial IQGAP1 regulates leukocyte transmigration by directing the LBRC to the site of diapedesis

2019 ◽  
Vol 216 (11) ◽  
pp. 2582-2601 ◽  
Author(s):  
David P. Sullivan ◽  
Prarthana J. Dalal ◽  
Fanny Jaulin ◽  
David B. Sacks ◽  
Geri Kreitzer ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Scaffold Protein ◽  
Interacting Proteins ◽  
Calponin Homology Domain ◽  
Directed Movement ◽  
Lateral Border ◽  
Leukocyte Transmigration ◽  
Calponin Homology ◽  
First Time

Transendothelial migration (TEM) of leukocytes across the endothelium is critical for inflammation. In the endothelium, TEM requires the coordination of membrane movements and cytoskeletal interactions, including, prominently, recruitment of the lateral border recycling compartment (LBRC). The scaffold protein IQGAP1 was recently identified in a screen for LBRC-interacting proteins. Knockdown of endothelial IQGAP1 disrupted the directed movement of the LBRC and substantially reduced leukocyte TEM. Expression of truncated IQGAP1 constructs demonstrated that the calponin homology domain is required for IQGAP1 localization to endothelial borders and that the IQ domain, on the same IQGAP1 polypeptide, is required for its function in TEM. This is the first reported function of IQGAP1 requiring two domains to be present on the same polypeptide. Additionally, we show for the first time that IQGAP1 in the endothelium is required for efficient TEM in vivo. These findings reveal a novel function for IQGAP1 and demonstrate that IQGAP1 in endothelial cells facilitates TEM by directing the LBRC to the site of TEM.

LYK4 is a component of a tripartite chitin receptor complex in Arabidopsis thaliana

2019 ◽  
Vol 70 (19) ◽  
pp. 5507-5516 ◽  
Author(s):  
De-Xing Xue ◽  
Chun-Lian Li ◽  
Zhi-Ping Xie ◽  
Christian Staehelin
Keyword(s):  
Arabidopsis Thaliana ◽  
Scaffold Protein ◽  
Receptor Complex ◽  
Chitin Receptor

LYK1, LYK4, and LYK5 form a tripartite receptor complex in Arabidopsis to perceive chitin, with constitutive LYK4–LYK5 and chitin-induced LYK1–LYK5 ectodomain interactions, and LYK4 functioning as a LYK5-associated co-receptor or scaffold protein.

scholarly journals Surface functions during mitosis. III. Quantitative analysis of ligand-receptor movement into the cleavage furrow: diffusion vs. flow.

1982 ◽  
Vol 93 (3) ◽  
pp. 950-960 ◽  
Author(s):  
D E Koppel ◽  
J M Oliver ◽  
R D Berlin
Keyword(s):  
Cell Shape ◽  
Single Cells ◽  
Effective Diffusion ◽  
Membrane Receptors ◽  
Cleavage Furrow ◽  
Receptor Complex ◽  
Con A ◽  
Surface Distribution ◽  
Lectin Receptor ◽  
Receptor Complexes

The surface distribution of concanavalin A (Con A) bound to cell membrane receptors varies dramatically as a function of mitotic phase. The lectin is distributed diffusely on cells labeled and observed between mid-prophase and early anaphase, whereas cells observed in late anaphase or telophase demonstrate a marked accumulation of Con A-receptor complexes over the developing cleavage furrow (Berlin, Oliver, and Walter. 1978. Cell. 15:327-341). In this report, we first use a system based on video intensification fluorescence microscopy to describe the simultaneous changes in cell shape and in lectin-receptor complex topography during progression of single cells through the mitotic cycle. The video analysis establishes that fluorescein succinyl Con A (F-S Con A)-receptor complex redistribution begins coincident with the first appearance of the cleavage furrow and is essentially complete within 2-3 min. This remarkable redistribution of surface fluorescence occurs during only a modest change in cell shape from a sphere to a belted cylinder. It reflects the translocation of complexes and not the accumulation of excess labeled membrane in the cleavage furrow: first, bound fluorescent cholera toxin which faithfully outlines the plasma membrane is not accumulated in the cleavage furrow, and, second, electron microscopy of peroxidase-Con A labeled cells undergoing cleavage shows that there is a high linear density of lectin within the furrow while Con A is virtually eliminated from the poles. The rate of surface movement of F-S Con A was quantitated by photon counting during a repetitive series of laser-excited fluorescence scans across dividing cells. Results were analyzed in terms of two alternative models of movement: a flow model in which complexes moved unidirectionally at constant velocity, and a diffusion model in which complexes could diffuse freely but were trapped at the cleavage furrow. According to these models, the observed rates of accumulation were attainable at either an effective flow velocity of approximately 1 micron/min, or an effective diffusion coefficient of approximately 10(-9) cm2/s. However, in separate experiments the lectin-receptor diffusion rate measured directly by the method of fluorescence recovery after photobleaching (FRAP) on metaphase cells was only approximately 10(-10) cm2/s. Most importantly, photobleaching experiments during the actual period of F-S Con A accumulation showed that lectin-receptor movement during cleavage occurs unidirectionally. These results rule out diffusion and make a process of oriented flow of ligand-receptor complexes the most likely mechanism for ligand-receptor accumulation in the cleavage furrow.

HIV-1 Nef Interferes with M-CSF Receptor Signalling through Hck Activation and Inhibits M-CSF Bioactivities.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1463-1463
Author(s):  
Seiji Okada ◽  
Shinya Suzu
Keyword(s):  
Mouse Model ◽  
Disease Progression ◽  
Molecular Complex ◽  
Myeloid Leukemia ◽  
Receptor Complex ◽  
Macrophage Differentiation ◽  
Physiological Conditions ◽  
Receptor Signalling ◽  
First Time ◽  
Hiv 1

Abstract HIV-1 Nef protein is a major determinant of the pathogenicity of the virus. It has been shown that Nef activates Hck, a member of Src family kinase, in monocytes/macrophages and that the interaction is critical for AIDS-like disease progression in a mouse model. However, it was unclear how the molecular interaction in monocytes/macrophages leads to the disease progression. Here, we show for the first time that Nef interferes with the M-CSF/M-CSF receptor pathway. In this study, we introduced a conditionally active Nef into myeloid leukemia TF-1-fms cells and analyzed their responsiveness to M-CSF. We found that Nef-activated Hck constitutively associated with M-CSF receptor complex. The formation of the molecular complex should occur under physiological conditions, i.e., upon M-CSF stimulation. Due to the aberrant molecular association, the tyrosine-phosphorylation/activation of the receptor in response to M-CSF was markedly diminished in Nef-active cells. Consequently, Nef activation caused the inhibition of M-CSF-mediated proliferation of TF-1-fms cells and macrophage differentiation of the cells induced by M-CSF and 12-O-tetradecanoylphorbol 13-acetate. These results indicate that HIV-1 Nef interferes with M-CSF receptor signalling through Hck activation and thereby inhibits M-CSF functions in monocytes/macrophages.

scholarly journals Time-dependence of biological activity induced by covalent insulin-receptor complexes in rat adipocytes

1985 ◽  
Vol 232 (1) ◽  
pp. 49-53 ◽  
Author(s):  
A Schüttler ◽  
C Diaconescu ◽  
D J Saunders ◽  
D Brandenburg
Keyword(s):  
Insulin Receptor ◽  
Inhibitory Effect ◽  
Receptor Complex ◽  
Half Time ◽  
Simple Method ◽  
Receptor Complexes ◽  
Maximal Stimulation ◽  
Monocomponent Insulin ◽  
Specific Receptors ◽  
Stimulation Of

Lipogenesis in isolated adipocyte preparations is stimulated when photosensitive insulin derivatives are attached covalently to specific receptors. This response was compared quantitatively with that to reversibly associated insulin, and it was shown that both covalent and reversible insulin-receptor complexes behave very similarly. The extent of stimulation of lipogenesis was studied as a function of time. Cells were incubated in buffer for various times before addition to vials containing 0 (basal) or 10 ng of monocomponent insulin/ml (maximal) and [U-3H]glucose. After 60 min, the toluene-soluble [3H]lipids were measured. The maximal stimulation induced by reversibly bound insulin was virtually constant over a period of 4 h. In contrast, adipocytes to which N alpha B2-(2-nitro-4-azidophenylacetyl)-des-PheB1-insulin had been covalently attached at the start of the experiment showed a loss of stimulation with time when incubated at 37 degrees C. This loss was decreased in the presence of lysosomotropic agents such as chloroquine at concentrations (approx. 200 microM) that had very little or no effect on the basal and maximal lipogenesis rates. A simple method was used to transform the measured rate of loss of stimulation into a rate of loss of effective units. A half-time of 80 min was calculated for the effective covalent insulin-receptor units in adipocytes at 37 degrees C at pH 7.4. This is very close to values reported by others for the internalization of covalent complexes in these cells, suggesting that this may be the causative event for the deactivation of the insulin-receptor unit. The inhibitory effect of chloroquine on the deactivation may indicate that the insulin-receptor complex can function even after internalization.

scholarly journals ATP-dependent activation of glucocorticoid receptor from rat liver cytosol

1980 ◽  
Vol 190 (3) ◽  
pp. 799-808 ◽  
Author(s):  
V K Moudgil ◽  
J K John
Keyword(s):  
Glucocorticoid Receptor ◽  
Rat Liver ◽  
Sodium Molybdate ◽  
Receptor Activation ◽  
Activation Process ◽  
Receptor Complex ◽  
Liver Cytosol ◽  
Receptor Complexes ◽  
Steroid Binding ◽  
Rat Liver Cytosol

The glucocorticoid—receptor complex from freshly prepared rat liver cytosol is in a non-activated form, with very little affinity to bind to isolated nuclei. When such preparations were incubated with 5—10 mM-ATP at 4 degrees C, the receptor complex acquired the properties of an ‘activated’ transformed form, which readily bound to nuclei, ATP—Sepharose, phosphocellulose and DNA—cellulose. This transformation was comparable with the activation achieved by warming the steroid—receptor complex at 23 degrees C. The effect of ATP was specific, as it was more effective than ADP, whereas AMP had no such effect on activation. The process of receptor activation was sensitive to the presence of 10 mM-sodium molybdate; the latter blocked activation by both ATP and heat. Bivalent cations had no observable effect on the receptor activation at low temperature, but they decreased the extent of activation by ATP. The steroid-binding properties of glucocorticoid receptor remained intact under the above conditions. However, a significant increase in steroid binding occurred when ATP was preincubated with cytosol receptor before the addition of [3H]triamcinolone acetonide. ATP also stabilized the glucocorticoid—receptor complexes at 23 degrees C. These results suggest a role for ATP in receptor function and offer a convenient method of studying the activation process of glucocorticoid receptor under mild assay conditions.

Sign in / Sign up

Export Citation Format

Share Document